Here are the most common causes of brown grass:
• Dryness. With the dry spell that followed all the rain we had this summer, most people are seeing drought stress in their lawn.
“Give it a good thorough watering and see if it greens up,” extension agent Rebecca McMahon said. If it doesn’t, the brown plants are dead, and you’ll need to overseed or otherwise repair those spots.
• Brown patch. Fescue lawns get brown patch when the weather is humid, days are hot, nights are warm, and the grass stays wet overnight, either from evening irrigation or a nighttime rain. To diagnose brown patch, look for brown lesions on grass blades. Generally, brown patch leaves no lasting damage, and no treatment is needed. Avoid fertilizing when conditions are ripe for brown patch, and water only in the morning so that the blades dry out by nighttime.
• Grubs. Give your brown grass a tug. If it comes up easily with no resistance, this can mean that the roots are no longer there because of the feeding of grubs underground. You should be able to roll back the turf like a rug and see grubs underneath. Damage shows up from late July through August. Apply a grub killer and water in immediately.
• Soil pH. Your soil may be too acidic or too alkaline. This happens especially with Bermuda and zoysia, and with Kentucky bluegrass that may be part of a fescue lawn (it turns yellow before it turns brown). You’ll need to get a soil test to know whether this is the problem, and then amend the soil accordingly.
• Large patch or spring dead spot. Large patch can show up on zoysia and buffalo in spring or fall, and spring dead spot on Bermuda and buffalo in the spring. No good fungicides are available. Don’t over-fertilize or overwater, especially in late summer, and try core-aerating or dethatching.